Fiber optic systems are commonly used for transmitting bits of data information. Because there are no practical optical computers, the bits of data information typically exist as electrical signals that are converted to optical (light) signals for transmission over optical fibers, and then converted from optical signals back to electronic signals for processing of the transmitted information. An optoelectronic light source converts an electrical signal to an optical signal that is then coupled to an optical fiber for transmission. The optical signal is decoupled from the optical fiber and received by an optoelectronic light detector for reverse conversion back to an electrical signal. In fiber optic systems, the optoelectronic light sources are typically vertical cavity surface emitting lasers (VCSEL) or light emitting diodes, and the optoelectronic light detectors are typically photo-intrinsic diodes (PINS) or avalanche photodiodes.
In a typical optical fiber based optical communication systems, an optoelectronic device having one or more components (i.e., light sources or light detectors) transmits optical signals to, or receives optical signals from, one or more optical fibers. The optical fibers are mounted in a fiber optic connector that positions the ends of the optical fibers in close proximity to the optoelectronic component. A lens is placed between the fibers and the components to focus light into or from the optical fibers. When transmitting, the optoelectronic device converts electrical signals into optical signals and directs the optical signals into the optical fibers. When receiving, the optoelectronic device receives the optical signals from the optical fibers and converts the optical signals into electrical signals.
To provide optimum transfer of an optical signal to or optimum reception of an optical signal from an optical fiber, the optoelectronic component must be precisely aligned in three dimensions relative to the lens, and the combination of the component and the lens must be precisely aligned in three dimensions relative to the end of the optical fiber. If the optical transmission path is not precisely aligned, the quality of the optical communication can be significantly degraded. The core of the optical fiber has cross-sectional dimensions in the order of a few microns to a few hundred microns, and the lens and the optoelectronic device elements have similar cross-sectional dimensions. Precisely aligning the optoelectronic device, the lens, and the core of the optical fiber can be difficult because of the small dimensions.
Therefore, an important step in building fiber optic transmitting and receiving modules for optical communication systems is aligning the optoelectronic component having an array of emitting surfaces with the lens array for optimal light transmission to and from the optical fibers. This alignment is on the three linear axes and a rotational axis to properly focus the light and align the optical paths between the multiple emitting (or receiving) surfaces and the multiple optical fibers to maximize signal strength.
Although devices and methods exist that are capable of achieving the required alignment precision in the range of several microns, such devices typically suffer from one or more shortcomings. The shortcomings typically involve passively aligning the components by individually assembling them in precisely defined positional relationships, with very close tolerances for each position. For example, the positional tolerance for the lens array is about five microns. In addition, multiple steps are often required to provide the required precision, and these steps often cannot be fully automated. If upon final assembly it is discovered that the components are not precisely aligned, the entire module must be discarded because the alignment typically cannot be adjusted once the components are assembled.
In view of the foregoing, there is a need for a simple, low-cost optoelectronic module and method of producing the same that allows an active alignment between the optoelectronic device, the lens array, and the optical fibers.